Susceptibility of 63 clinical isolates of Klebsiella (K.) pneumoniae to various metals and antibiotics was determined. Eighteen of them were found to be resistant to both fluorescein mercuric acetate (FMA) and HgCl2. It was clear that resistance to FMA of K. pneumoniae JK9 was induced by exposure to subinhibitory concentration of FMA and the antibacterial activity of FMA was lost by incubation with FMA resistant strains. It was also suggested that FMA-inactivating enzyme was inductively produced by preincubation with FMA.
This indicates that a new type of FMA-resistance mechanism in K. pneumoniae clinically isolated was found out.
